Date post: | 18-Dec-2015 |
Category: |
Documents |
Upload: | theodore-greene |
View: | 213 times |
Download: | 0 times |
THE SIERRA NEVADA THE SIERRA NEVADA MOUNTAINSMOUNTAINS
Only the end• Of 400 million years of history
Miscellaneous epeiric seas
• From about 600 my BP
THE THREE SIERRASTHE THREE SIERRAS
• ~ 250 – 150 million years = 1st Sierras
• ~ 120 – 60 million years = 2nd Sierras
• ~ 20 my – present = 3rd Sierras
1st SIERRAS
1ST SIERRAS
• Timing - ~ 250 – 150 my
• Part of Pangea
• Subduction formed
• Little evidence– Later intrusion and metamorphism– Erosion (twice)
2nd SIERRAS
2ND SIERRAS
• Timing -~ 120-60 my
• N.A. separated and moving westward
• Subduction formed
• Evidence partially destroyed by erosion
Plate motions and the 2nd Sierras
40my of erosion to the 2nd Sierras
• ~60-20 my• no subduction• erosion
3rd SIERRAS
Block faulting to formthe 3rd Sierras
• ~20 my – eastern part southern block is uplifted; internal faulting at 12 my; ?uplift at ~9 my
• ~9 my – main block is tilted to west
• Erosion continued for 20 my but slightly different on the two blocks
N
Details about the blocks
• Details are dependent on datable lavas and pyroclastic material, or
• on dateable terminal sediments of the Kern River.
• Not much and not much done!
Erosion on the 3rd Sierras
• Streams until the ice ages– Main block – E and W after 9 my tilting– Southern block – S by the Kern River ?60 my
to present
• Valley glaciers off and on 1.6 my to present for the higher parts
Kern River-1Kern River-1 Controlled by ancient fault dating back to 2Controlled by ancient fault dating back to 2ndnd
SierrasSierras Fault = Kern Canyon FaultFault = Kern Canyon Fault Located primarily on Southern blockLocated primarily on Southern block TimingTiming
60 – 20 my, Mt. Whitney to Kernville to Colorado 60 – 20 my, Mt. Whitney to Kernville to Colorado RiverRiver
20 – 12 my, Mt. Whitney to Kernville to Caliente 20 – 12 my, Mt. Whitney to Kernville to Caliente Creek to Bena to San Joaquin ValleyCreek to Bena to San Joaquin Valley
12 – present, Mt. Whitney to Kernville to lower 12 – present, Mt. Whitney to Kernville to lower Kern River to San Joaquin ValleyKern River to San Joaquin Valley
Kern River-2Kern River-2 Current Current
topographytopography
Kern River-3Kern River-3
60 -20 my60 -20 my Topography Topography
much much differentdifferent
Empties Empties into into Colorado Colorado River to ERiver to E
Kern River-4Kern River-4
20 – 12 my20 – 12 my Topography Topography
differentdifferent Empties into Empties into
San Joaquin San Joaquin basin SE of basin SE of Bakersfield Bakersfield (Bena)(Bena)
Kern River-5Kern River-5
12 – present12 – present Topography Topography
similarsimilar Empties into Empties into
San Joaquin San Joaquin basin basin toward toward BakersfieldBakersfield
Kern River-6Kern River-6
Ancient Lake Ancient Lake Isabella – Isabella – northnorth
Walker Lake – Walker Lake – southsouth
not on Kern not on Kern R.R.
12 - ~1 my12 - ~1 my
ECONOMIC ECONOMIC RESOURCESRESOURCES
TOURISM
• Summer – hiking, backpacking, rock climbing, camping, boating, fishing, sightseeing, (in selected areas) hunting
• Winter – skiing– Mammoth area– Donner Pass area– Several other smaller areas
GOLD-1
• Foothills E of Sacramento
GOLD-2
• DEEP HYDROTHERMAL VEINS EXPOSED BY 60+ MY OF EROSION—1850’s, 1930’s, 1980’s
• PLACER DEPOSITS BY 60+ MY OF STREAM SORTING AND DEPOSITION—1850’s, 1930’s
TUNGSTEN
• DEEP HYDROTHERMAL VEINS EXPOSED BY 60+ MY OF EROSION
• Hydrothermal fluids + CaCO3
• Primarily WWII
SOUTHERN GEM MINES
• Tourmaline, beryl, and garnet
• From the ‘shallow’ pegmatites of San Diego and Riverside counties
• Varied depending on price for gems—1920’s empress of China bought quantities of tourmaline
• Fine mineral samples
facetted tourmaline (boron)facetted tourmaline (boron)
Rough beryl (beryllium)Rough beryl (beryllium)
Cut garnets (various)Cut garnets (various)
pegmatite
• An odd igneous rock
• It contains concentrations of rare elements and forms rare minerals